Oviductin (Muc9) is expressed in rabbit endocervix

While isolating and characterizing cervical mucin glycoproteins, oviductin (Muc9) was identified in the rabbit endocervix. Following tissue homogenization, endocervical proteins were fractionated by exclusion chromatography (Sepharose CL-4B). High molecular weight components of the void volume were resolved by density gradient centrifugation using cesium bromide and dissociative conditions (4 M guanidinium chloride). High density fractions (rho = 1.40 - 1.56 g/ml) were deglycosylated with anhydrous trifluoromethane sulfonic acid and sent to Harvard Microchemistry where in situ digestion and tryptic peptide separation were performed. Out of an HPLC map, microsequence (KLIMGFPTYGR) from peak 51 was 100% identical to mouse oviductin, and microsequence (KSTGHNFPLP) from peak 70 was 90% identical to hamster oviductin. Temporal expression of oviductin transcripts (2.4-kilobase) was negligible during the first three months of postnatal cervical differentiation. Transcripts were minimally detectable in the cervices of 4-month-old juveniles. Strong expression in the endocervices of adults was eliminated by ovariectomy and restored by estrogen treatment. The presence of oviductin in the rabbit endocervix indicates this glycoprotein may have multiple functions, and it can no longer be considered oviduct-specific.